Process of liquefying air and separating out oxygen.



R. MEWES. PROCESS 0F LIQUEFYING AIR AND SEPARATING OUT OXYGEN.

APPLICATION FILED MAR. 2, 1906.

Patented Ja11.3, 1911.

In wlzor:

RUDOLF MEWES, or BERLN, GERMANY.

PROCESS 0F LIQUEFYING AIR AND SEPARATNG OUT OXYGEN.A

Specification of Letters Patent.

Patented aan'. s, i911.

Application filed March2, 1906. Serial No. 303,800.

-of liquefying air and separating gases with a partial recovery of the energy consumed by the compression. It differs from older and similar processes very m-aterially in that respect that for the purpose of -reducing the pressure behind the expansion chamber in the exhaust port of the expansion engines (piston engines, Laval or Parsons turbines or the like) the expanded gases are not sucked ofi' by the compressor, but by a special device (suction pump or the like), thus producing a partial vacuum in order not to let cold expanded gases renter into the compressor, but to drive them out into the open air after using them as far as possible as a cooling medium for the process itself, in order to obtain in this way a mixture of fluids rich in oxvgen. This is greatly facilitated by not sending back the expand- .cd gases into the circuit, but bv driving them out after an almost perfect exchange of heat has taken place. ',lhe new technical effects gained in this way over older processes for liquefying air in which the expanded gases, after having donc their work, are led off under atmospheric pressure. consist in the first place thereintl'lat. in couscquence of the greater lowering of the pressure, the falling of the temperature is correspondingly greater, that secondly the engine is not stopped as is the case with Siemens and other similar devices by a great lowering of the temperature, but thirdly also therein that the liquefied gases, which are partly evaporated again in the. process itself, are evaporated at al suitably reduced pressure of less than one atmosphere. and in quantities corresponding with the vapor teusions of the component parts of the mixture of fluids'. For instance` as experiments by Dewar, Estreicher, Baile, Olszewski have shown. (conf. Zeitschrift fr Komp-rmz'crtc und Flssig@ Gase, 2nd year. number 12, page 180) nitrogen has at 195 C. a vapor tension of 740 mm., oxygen a tension of 142 mm. By producing a reduced pressure above a fluid thel temperature isl at once lowered, if sufficient heat is not admitted for the evaporation of the quantities of fluids sucked off. It is evident that,-as in the present process the temperature, by producing a reduced pressure by means of a suction pump. can easily be lowered down to -2000 or still farther, and as at these temperatures the proportion of the vapors of both fluid parts is greater than 7410/142, therefore greater than 5`it is necessary to evaporate over five times as much nitrogen as oxygen. This proportion becomes greater with the lowering of the temperatureandis according to Olszewski at 214:o /3.8,

or 16. By producing a vacuum of 60 mm.,

which is technically easy, 16 times as much nitrogen as oxygen will be evaporated, therefore leaving nearly pure oxygen. The process is therefore suited for separating out directly almost pure liquid oxygen, and by its distillation correspondingly pure gaseous oxygen.

The arzcompanying; drawing shows in Figure l a diagrammatic view of a 'plant for the liquefaction of air according to the present process, and in Fig. l an example of.k

the fluid separator.

In the compression cylinder y] all the gas sucked into it, and which previously has been freed of moisture, is compressed while being cooled as far as possible to, for instance. 5 atmospheres and pressed into the reservoir From the .reservoir Z) one of the compression cylinders c, provided with a cooling jacket c, which cylinder is -to be of a suitable size, sucks in a pa rt of the compressed gas, and colnpresses the same to 25 atmospheres, and presses the high tension gas into the jacket f of the expansion cylinder (l, which is fed from the reservoir b and expandsA a part of the gas compressed to 5 atmospheres and thereby does usefulY work.

In consequence of this a great lowering of the temperature takes place, whereby the walls of the cylinder and also the high tension gases in the cylinder jacket f are greatly cooled. The exhaust gases of the expansion cylinder Z pass into an insulated box, which surrounds the cylinder, from which they are carried off by a suction pump into the open air, so that behind the outlet of the ylinder Z the pressure is below the atmospheric, and with this lowering of the pressure the lowering of the temperature is increased. A part of the high tension gas,.cooled in the jacket f, is now led into the second expansion cylinder 7c through the pfpe z' which passes through the box t, and i1. further cooled in its passage through the bos- -t by the cold gases coming from the cylinder cl. The air expanded in the cylinder ,7c escapes through the pipe 0 into the finishing cooler p. lhe other part of the high tension gases, greatly cooled in j, is led ott', throughthe conduit l, into the jacket m of the cylinder Ic and, after being cooled here, through the pipe n into another cooler p, through which the tube n passes in spiral windings s. The cold exhaust gases, on leaving the apparatus, effect in consequence of this device a still further cooling of the high tension gases and are then led into thc box q, which surrounds the finishing cooler y) and the second expansion cylinder together with the pipes 'n and o, and are sucked ott' frein this box through the suction pump r together with thev exhaust gases of the first expansion cylinder (l, so that also behind the out-let of the cylinder the pressure is beloivthe atmospheric, the lowering of the pressure is therefore still considerably greater as in the first case and consequently also the lowering of the temperature. The high tension air or gas liquefied in the spiral s of the pipe n is caused to enter through a tluid separator 'u of any suitable nature into the finishing cooler 10. In Fig. l a fluid separator suitable for the purpose is shown. lt consists of a closed vessel in which a float valve o is adapted by rising to open the valve 'w 'through the agency of the rod ze. lWhen the valve w is opened the liquid air accumulated in the closed vessel flows down through thepipe ai into p, from which it passes through the pipe z/ into the box q, in Which the pressure is maintained below that of the atmosphere by means ofy a spiral suction pump r (Fig.

.1), so that through the evaporation of a @sosia of new fresh liquid air, so that a duid mixture is directly obtained, which is almost pure, or very rich in, oxygen, and which can be used as such at once, or for the production of gaseous oxygen according to any existing process for the separation of gases. YThe liquid oxygen is drawn off through the cock 'a'.

What l claim as my invention and desire to secure by UnitedStates Letters Patent 1s l. kA proeess for liquefying 'air and separating out oxygen Which comprises compressing air into a` reservoir, cooling the saine, expanding said compressed air into a raretied space, and maintaining the rarefaction of said space by continuously removing said expanded air Without completing the cycle, substantially as, and for the purpose, set forth.

2. The hereinbefore described process, which consists in compressing air into a reservoir, and cooling the saine, further cornpressin T a. part of said compressed air cooling sai` further compressed part by the expansion of the other part of said compressed air, cooling a part of said further compressed air by the expansion of another part thereof, and exhausting said expanded air into a vacuum, substantially as, and for the purpose, set forth. e

'3. lThe hereinbefore described process Which consists in compressing air into a reservoir and simultaneously cooling the same, furtherv compressing a part of said cornpressed air, cooling said further compressed air by the expansion of` the other part of said compressed air, exhausting the said expandedpart of the compressed air into a rarefied space` further cooling the further compressed air by the expansiouof a part thereof, and expanding said further com! pressed air and the said expanded part thereof into a raretied space, substantially as, and for the purpose, set forth.

ln testimony whereof have signed my name to this specification in the presence of two subscribing witnesses.

RUDOLF MEWES.- l/Vitnesses:

' VVOLDEMAR HAUPT, Huisnr Hasruu. 

